Automatic shifting power transmissions, both planetary and countershaft type, have hydraulic controls systems for effecting the establishment and disestablishment of power paths through the gearing in the transmission. The power paths include fluid operated friction devices, such as clutches and brakes, for connecting the appropriate gear components to the power source; i.e., the prime mover, or to ground; i.e., transmission housing.
When a ratio interchange is being made, at least one friction device is being engaged to establish the power path. Hydraulic timing devices are used to control the engagement rate of the on-coming friction device. The timing devices include accumulators which are filled with hydraulic fluid simultaneously with a fluid motor of the friction device. These accumulators require space within the transmission and the installation of pistons, springs and covers at assembly.
There are accumulators in the form of self-contained assemblies that can reduce the assembly time and cost. These devices do not reduce the number of accumulators nor the space required. As a general rule, each friction device has an accumulator, such that six friction devices require six accumulators.